US7406221B2 - Two-dimensional photonic crystal multiplexer/demultiplexer - Google Patents

Two-dimensional photonic crystal multiplexer/demultiplexer Download PDF

Info

Publication number
US7406221B2
US7406221B2 US10/566,843 US56684304A US7406221B2 US 7406221 B2 US7406221 B2 US 7406221B2 US 56684304 A US56684304 A US 56684304A US 7406221 B2 US7406221 B2 US 7406221B2
Authority
US
United States
Prior art keywords
point
defect
wavelength
waveguide
optical input
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
Application number
US10/566,843
Other languages
English (en)
Other versions
US20060204161A1 (en
Inventor
Susumu Noda
Takashi Asano
Yoshihiro Akahane
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Japan Science and Technology Agency
Sumitomo Electric Industries Ltd
Original Assignee
Japan Science and Technology Agency
Sumitomo Electric Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Japan Science and Technology Agency, Sumitomo Electric Industries Ltd filed Critical Japan Science and Technology Agency
Assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD., JAPAN SCIENCE AND TECHNOLOGY AGENCY reassignment SUMITOMO ELECTRIC INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: AKAHANE, YOSHIHIRO, ASANO, TAKASHI, NODA, SUSUMU
Publication of US20060204161A1 publication Critical patent/US20060204161A1/en
Application granted granted Critical
Publication of US7406221B2 publication Critical patent/US7406221B2/en
Expired - Fee Related legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1225—Basic optical elements, e.g. light-guiding paths comprising photonic band-gap structures or photonic lattices

Definitions

  • the present invention relates to a two-dimensional photonic crystal multiplexer/demultiplexer used for wavelength division multiplexing communication or other techniques. Particularly, it relates to a technique for improving the multiplexing/demultiplexing characteristics.
  • WDM wavelength division multiplexing
  • This technique requires an optical multiplexer and an optical demultiplexer, or wavelength filters, for mixing multiple wavelengths of light at the inlet of the transmission line and then separating the mixed light into each wavelength of light at the outlet.
  • An example of conventional demultiplexers is arrayed waveguide grating.
  • arrayed waveguide gratings currently used are somewhat oversized, as large as roughly several square centimeters.
  • a photonic crystal is a functional material having a cyclic distribution of refractive index, which provides a band structure with respect to the energy of light.
  • This device is particularly featured in that it has an energy region (called the photonic bandgap) that does not allow the propagation of light.
  • Introduction of an appropriate defect into the distribution of refractive index in the photonic crystal creates an energy level (called the defect level) due to the defect within the photonic bandgap. This allows only a specific wavelength of light having an energy corresponding to the defect level to exist within the wavelength range corresponding to the energy levels included in the photonic bandgap.
  • Forming a linear defect in the crystal provides a waveguide, and forming a point-like defect in the crystal provides a resonator.
  • the shape of the defect determines a wavelength, called the resonance wavelength, at which the resonance of light takes place.
  • Non-Patent Document 1 discloses the result of a computer simulation of a photonic crystal composed of infinitely long cylindrical elements made of a high refractive index material and arranged in a square lattice pattern. This construction allows light to be controlled by the photonic bandgap within a plane parallel to the square lattice. However, it does not enable the control of light in the direction perpendicular to the aforementioned plane. Photonic crystals having such a construction are impractical.
  • Patent Document 1 discloses a photonic crystal having a plate-shaped body in which plural areas having a refractive index different from that of the body (called the “modified refractive index area” hereinafter) are cyclically arranged to create a cyclic distribution of refractive index.
  • This construction can control light within the body because a photonic bandgap is present within the plane of the body and the difference in refractive index between the body and the surrounding air confines light within the body in the direction perpendicular to the body.
  • a waveguide is formed by eliminating the modified refractive index areas along a line ([0025], FIG. 1 ), and a point-like defect is formed by eliminating the modified refractive index areas within a point-like region ([0029], FIG.
  • Patent Document 1 shows a two-dimensional photonic crystal having modified refractive index areas, each consisting of a cylindrical hole, cyclically arranged in a triangular lattice pattern, where the diameter of one of the cylindrical holes located in the proximity of the waveguide is increased to be a point-like defect.
  • Non-Patent Document 1 S. Fan et al., “Channel Drop Tunneling through Localized States”, Physical Review Letters, (US), American Physical Society, 1998, vol. 80, pp. 960-963
  • Patent Document 1 Japanese Unexamined Patent Publication No. 2001-272555 ([0025], [0029], FIG. 1)
  • This type of two-dimensional photonic crystal can function as a demultiplexer for separating a ray of light whose wavelength equals to the resonance wavelength of the point-like defect from the light including plural wavelengths superimposed and propagating through the waveguide, and for emitting the light through the point-like defect to the outside. It can also function as a multiplexer that introduces, from the outside of the crystal, a ray of light whose wavelength equals to the resonance wavelength of the point-like defect into superimposed light propagating through the waveguide.
  • one and the same two-dimensional photonic crystal can function as a multiplexer and as a demultiplexer.
  • Such a two-dimensional photonic crystal is called the “multiplexer/demultiplexer” in this specification.
  • Creating plural point-like defects having different shapes in the proximity of the waveguide provides a multiplexer/demultiplexer in which each point-like defect multiplexes or demultiplexes a ray of light having a different wavelength.
  • each point-like defect multiplexes or demultiplexes a ray of light having a different wavelength.
  • the plural wavelengths of light each carries a different signal, it is possible to extract a specific signal from the transmission line (i.e. the waveguide) with the demultiplexer or introduce a specific signal into the transmission line with the multiplexer.
  • the point-like defect multiplexes or demultiplexes not only the ray of light having its resonance wavelength, ⁇ 0 , but also other rays of light included within a certain wavelength range around the resonance wavelength ⁇ 0 by certain percentages.
  • the multiplex/demultiplex spectrum takes the form of a Lorenz function around the resonance wavelength ⁇ 0 , as shown in FIG. 1 .
  • a multiplex/demultiplex spectrum expressed by a Lorenz function has a sharp peak; the value of the multiplex/demultiplex spectrum rapidly falls as the distance from the resonance wavelength ⁇ 0 increases, and it forms a long tail as the distance becomes much larger.
  • Such a multiplex/demultiplex spectrum expressed by a Lorenz function is accompanied by two problems to be solved with respect to the multiplexing/demultiplexing operations.
  • the first problem results from the sharpness of the peak of the multiplex/demultiplex spectrum.
  • An aged deterioration or a temperature change in the waveguide 66 have the same transmission wavelength band because they are identically shaped.
  • the difference in cycle between the forbidden band zones 63 and 64 produces a wavelength band 75 that is included within the transmission wavelength band 73 of the waveguide in the forbidden band zone 63 but not within the transmission wavelength band 74 of the waveguide in the forbidden band zone 64 .
  • the two cycles can be appropriately determined so that the resonance wavelength of the point-like defects 67 and 68 falls within the wavelength band 75 .
  • the light having the resonance wavelength and propagating through the input waveguide 65 is reflected at the boundary between the forbidden band zones 63 and 64 .
  • the demultiplexing efficiency is enhanced.
  • a demultiplexed ray of light is introduced through the point-like defects 67 and 68 into the output waveguide 66 , the light is reflected at the boundary between the forbidden band zones 63 and 64 and extracted from only one end of the output waveguide 66 . This also contributes to the enhancement of the demultiplexing efficiency. system used may cause an error in the wavelength of light propagating through the waveguide or in the resonance wavelength of the multiplexer/demultiplexer.
  • the second problem results from the long tail of the multiplex/demultiplex spectrum. Presence of such a long tail will allow rays of light having wavelengths far from ⁇ 0 to be undesirably mixed, thus causing a noise. Also, the tail may overlap the wavelength of the signal of an adjacent channel, causing a crosstalk between the two signals.
  • the present invention intends to provide a two-dimensional photonic crystal multiplexer/demultiplexer capable of preventing the multiplexing/demultiplexing efficiency from deteriorating due to an error of the input signal or the resonance wavelength, and also suppressing the crosstalk caused by the tail of the multiplex/demultiplex spectrum, each problem being attributable to the peak shape of the multiplex/demultiplex spectrum of each point-like defect.
  • the present invention provides a two-dimensional photonic crystal multiplexer/demultiplexer, which is characterized by:
  • a first optical input/output section consisting of a waveguide formed in the body, where the waveguide is made of a linear defect of the modified refractive index areas;
  • the two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention has a body consisting of a slab, or a thin plate whose size in the in-plane direction is much larger than its thickness.
  • This body is provided with areas (i.e. the modified refractive index areas) having a refractive index different from that of the body and being arranged in a lattice pattern with a predetermined cycle.
  • This construction provides a two-dimensional photonic crystal having a photonic bandgap that prevents rays of light within a specific wavelength band determined by the aforementioned cycle from passing through the body along the in-plane direction.
  • the lattice pattern for arranging the modified refractive index areas are triangular lattice patterns and square lattice patterns.
  • the refractive index of the modified refractive index areas may be higher or lower than that of the body.
  • the modified refractive index areas may be holes arranged in a cyclic pattern in the body. This construction is preferable because it produces a large difference in refractive index between the areas and the body. Another point is that it is easy to manufacture.
  • the body is provided with a first optical input/output section consisting of a waveguide made of a linear defect of the modified refractive index areas.
  • the waveguide is formed by eliminating the modified refractive index areas, or by omitting the modified refractive index areas, along a line.
  • the waveguide functions as an optical input section for introducing light including plural wavelengths superimposed into the demultiplexer if it is used as a demultiplexer, or as an optical output section for extracting light including plural wavelengths superimposed to the outside if it is used as a multiplexer.
  • the body is also provided with a second optical input/output section.
  • This section functions as an optical output section for extracting light having a specific wavelength to the outside of the crystal if it is used as a demultiplexer, or as an optical input section for introducing light having a specific wavelength into the multiplexer if it is used as a multiplexer.
  • the second optical may be either a waveguide or a point-like defect.
  • a second optical input/output section taking the form of a point-like defect can be formed by creating a point-like region devoid of the modified refractive index areas. The point-like defect can be obtained by making the size of one of the modified refractive index areas different from that of the others or by eliminating one of these areas.
  • the point-like defect composed of two or more modified refractive index areas adjacent to each other.
  • the set of modified refractive index areas is regarded as a single point-like defect.
  • Q-value is an index that represents the performance of a resonator, which, by definition, is inversely proportional to the percentage of the amount of energy leaking from the resonators per unit of time. Accordingly, a larger Q-value will reduce the amount of energy of light leaking from the resonator.
  • a second optical input/output section taking the form of a waveguide can be formed by the same method as used for forming the waveguide of the first optical input/output section. It is also possible to add one or more point-like defects in the proximity of the waveguide of the second optical input/output section so that light can be extracted from the waveguide via the point-like defect to the outside of the crystal, or introduced into the multiplexer through the point-like defect.
  • two or more point-like defect resonators having substantially the same resonance wavelength are arranged in series. For example, they can be arranged along the direction perpendicular to the waveguide of the first optical input/output section, along a direction at an angle to the waveguide, or in a zigzag pattern.
  • the point-like defect resonators can be formed by the same method as used for forming the point-like defect of the aforementioned optical input/output section.
  • the point-like defect resonators which do not directly introduce or emit light from or to the outside, should be preferably designed so that it allows only a small amount of light to leak to the outside of the crystal.
  • a donor type defect formed by creating a region devoid of the modified refractive index areas, or by omitting the modified refractive index areas, is more suitable for the point-like defect resonators than an acceptor type defect obtained by increasing the size of one of the modified refractive index areas because the donor type yields a higher Q-value (Q v ) between each point-like defect resonator and the outside of the crystal than that obtained with the acceptor type.
  • the value Q v can be further increased by shifting the modified refractive index area within the proximity of the point-like defect resonators from the position determined by the arrangement cycle.
  • the point-like defect formed by eliminating three modified refractive index areas located adjacent to each other on a straight line. Then, Q v ⁇ 5200 if there is no shift of the modified refractive index areas, whereas Q v ⁇ 45000 if two modified refractive index areas located closest to the point-like defect are shifted.
  • Light is transmitted between the first optical input/output section and the point-like defect resonator closest to the first optical input/output section, between each pair of adjacent point-like defect resonators, and between the second optical input/output section and the point-like defect resonator closest to the second optical input/output section.
  • the Q-value determined by the components concerned and their distance will be an index of the transmission of light.
  • the two-dimensional photonic crystal optical multiplexer/demultiplexer constructed as described above functions as either a multiplexer or a demultiplexer as follows. Firstly, the operation of a demultiplexer for separating a ray of light having a predetermined wavelength from light including plural wavelengths superimposed is described. When the superimposed light is propagated through the waveguide of the first optical input/output section, the point-like defect resonator closest to the waveguide traps only a ray of light whose wavelength equals to the resonance wavelength of the point-like defect resonators from the superimposed light. The trapped light is then successively captured by the adjacent point-like defects and finally reaches the second optical input/output section, which emits the light to the outside of the crystal.
  • a ray of light whose wavelength equals to the resonance wavelength of the point-like defect resonators is introduced into the second optical input/output section and then successively trapped by the point-like defect resonators in the opposite order.
  • the trapped light finally reaches the waveguide of the first optical input/output section, where it is mixed into the superimposed light propagating through the waveguide.
  • the spectrum of the light multiplexed or demultiplexed by the multiplexer/demultiplexer according to the present invention is examined. This examination assumes that there are two point-like defect resonators located between the two optical input/output sections, as shown in FIG. 2A .
  • the multiplex/demultiplex spectrum obtained with a conventional multiplexer/demultiplexer having only one point-like defect resonator between the two optical input/output sections, as shown in FIG. 2B is also examined.
  • Q in denote both the Q-value between the first optical input/output section and the point-like defect resonator closest to that section and the Q-value between the second optical input/output section and the point-like defect resonator closest to that section.
  • Q v denote the Q-value between each of the point-like defect resonators and the outside of the crystal.
  • the mutual coupling coefficient between the two point-like defect resonators is denoted by ⁇ .
  • I ⁇ ⁇ ( ⁇ ) 1 ⁇ e 2 ⁇ 2 ⁇ [ ⁇ ( 1 ⁇ 0 + 1 ⁇ e ) 2 + ⁇ 2 ⁇ 2 + 2 ⁇ ⁇ ⁇ ( 1 ⁇ 0 + 1 ⁇ e ) 2 - ⁇ 2 ⁇ ⁇ ( ⁇ - ⁇ 0 ) 2 + ( ⁇ - ⁇ 0 ) 4 ] ( 1 )
  • the conventional multiplexer/demultiplexer shown in FIG. 2B has only one point-like defect resonator 17 between the first optical input/output section 15 consisting of a waveguide and the second optical input/output section 16 consisting of another waveguide having the same structure.
  • the multiplex/demultiplex spectrum is calculated as follows:
  • I ⁇ ⁇ ( ⁇ ) 1 ( ⁇ e ⁇ 0 + 2 ) 2 + ⁇ e 2 ⁇ ( ⁇ - ⁇ 0 ) 2 ( 2 )
  • Equation (2) is an expression of the Lorenz type multiplex/demultiplex spectrum described earlier; it has a term of frequency ⁇ 2 in the denominator.
  • the denominator in equation (1) includes an ⁇ 4 term in addition to an ⁇ 2 term.
  • the ⁇ 4 term helps the value of the multiplex/demultiplex spectrum to increase within a range close to the resonance frequency ⁇ 0 and decrease within a range far from ⁇ 0 .
  • the multiplex/demultiplex spectrum takes (i) larger values within a range close to ⁇ 0 and (ii) smaller values within a range far from ⁇ 0 , compared to that of the conventional multiplexer/demultiplexer.
  • the solid lines correspond to equation (1) and the broken lines correspond to equation (2).
  • the resonance wavelength ⁇ 0 is 1550 nm.
  • FIG. 3B is an enlarged view of FIG. 3A .
  • the two-dimensional photonic crystal optical multiplexer/demultiplexer yields the following effects: (i) The multiplex/demultiplex spectrum takes larger values within a range close to ⁇ 0 . Even if the frequency ⁇ 1 of the light propagating through the waveguide is shifted from the resonance frequency ⁇ 0 for some reason, such as an error in the wavelength of the light propagating through the waveguide or an error of the resonator, the multiplex/demultiplex spectrum maintains a large value at frequency ⁇ 1 . Therefore, the multiplexing/demultiplexing efficiency becomes higher than that of the conventional multiplexer/demultiplexer.
  • the multiplex/demultiplex spectrum becomes flattened at around the resonance frequency ⁇ 0 , as shown in FIGS. 3A and 3B .
  • the flattened shape of the multiplex/demultiplex spectrum is referred to as the “flattop.”
  • the multiplex/demultiplex spectrum takes smaller values within a range far from ⁇ 0 . This prevents undesired wavelengths of light from being mixed into the multiplexed or demultiplexed light and thereby causing a noise. It also suppresses the crosstalk caused by the overlapping of the signal frequency of an adjacent channel.
  • the value of the multiplex/demultiplex spectrum at a frequency shifted from the resonance frequency ⁇ 0 by 0.005% is equal to or larger than ⁇ 1 dB (or 79%) of the value at ⁇ 0 .
  • the ratio of ⁇ 2 to [( ⁇ 0 /2) ⁇ (1/Q in +1/Q v )] 2 i.e. ⁇ 2 /[( ⁇ 0 /2) ⁇ (1/Q in +1/Q v )] 2 , should be preferably 0.2 ⁇ 10. This ratio is called the “coupling ratio” in this specification.
  • the above-described model illustrated the case where there are two point-like defect resonators and the second optical input/output section is a waveguide.
  • the aforementioned number may be increased from two to N, in which case the term of ⁇ 2N will work in the same manner as in the case of the previous model.
  • the distance between the first and second optical input/output sections is large, it is advantageous to provide more than two point-like defect resonators to connect the two sections. If more than two point-like defect resonators are used, it is necessary to individually design the point-like defect resonators so that they have the same resonance frequency and the same Q-value because each point-like defect resonator has a different relationship with the surroundings.
  • the second optical input/output section is a point-like defect
  • the second optical input/output section is a waveguide
  • This arrangement establishes the same relationship between each of the two point-like defect resonators and the surroundings, allowing the use of the same type of point-like defect resonators to obtain the same resonance frequency and the same Q-value. This facilitates the designing of the multiplexer/demultiplexer.
  • the first input/output section and/or the second optical input/output section with a reflecting section for reflecting light whose wavelength equals to the resonance wavelength of the point-like defect resonators.
  • the first optical input/output section provided with the reflecting section the light that has not been introduced into the point-like defect resonators but has passed by the resonators will be reflected by the reflecting section and then introduced into the resonators.
  • An appropriate distance setting between the point-like defect resonators and the reflecting section will cause a destructive interference between the light reflected by the point-like defect resonators and the light reflected by the reflecting section, thereby attenuating them.
  • Providing the second optical input/output section with the reflecting section will allow the extraction or introduction of light to be performed only at one end of the waveguide of the second optical input/output section.
  • the reflecting section can be constructed as follows: Initially, the body is divided into plural zones (called the “forbidden band zones”), with modified refractive index areas being formed within each forbidden band zones with a different arrangement cycle. Then, the first optical input/output section or the second optical input/output section is formed so that it passes through all the forbidden band zones.
  • the transmission wavelength band of the waveguide changes depending on the cycle of the modified refractive index areas.
  • each forbidden band zone can be appropriately determined so that the resonance wavelength of the point-like defect resonators falls within the transmission wavelength band of the waveguide of the first or second optical input/output section in a forbidden band zone including the point-like defect resonators, whereas it is out of the transmission wavelength band of the waveguide in any other forbidden band zone.
  • This construction prevents the light having the resonance wavelength from propagating through the waveguide in the other forbidden band zones; the light will be reflected at the boundary between the forbidden band zone concerned and an adjacent forbidden band zone.
  • the boundary functions as the reflecting section.
  • a structure having plural forbidden band zones described above is called the “heterostructure” in this specification.
  • FIG. 4 shows the first optical input/output section 11 having a first reflecting section 18 and the second optical input/output section 12 having a second reflecting section 19 .
  • the multiplex/demultiplex spectrum I( ⁇ ) is given by:
  • I ⁇ ⁇ ( ⁇ ) 4 ⁇ e 2 ⁇ 2 ⁇ [ ⁇ ( 1 ⁇ 0 + 1 ⁇ e ) 2 + ⁇ 2 ⁇ 2 + 2 ⁇ ⁇ ⁇ ( 1 ⁇ 0 + 1 ⁇ e ) 2 - ⁇ 2 ⁇ ⁇ ( ⁇ - ⁇ 0 ) 2 + ( ⁇ - ⁇ 0 ) 4 ] ( 3 )
  • FIG. 1 is an illustration for explaining problems relating to the multiplex/demultiplex spectrum of a conventional two-dimensional photonic crystal multiplexer/demultiplexer.
  • FIG. 2A is a schematic diagram of a two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention
  • FIG. 2B is another two-dimensional photonic crystal multiplexer/demultiplexer as a comparative example having only one point-like defect resonator.
  • FIGS. 3A and 3B are graphs showing an example of the multiplex/demultiplex spectrum of a two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention.
  • FIG. 4 is a schematic diagram of a two-dimensional photonic crystal multiplexer/demultiplexer having a heterostructure.
  • FIG. 5A is a perspective view and FIG. 5B is a plan view of an embodiment of the two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention.
  • FIG. 6 is a plan view for explaining the point-like defect of the two-dimensional photonic crystal multiplexer/demultiplexer of the aforementioned embodiment.
  • FIG. 7 is a schematic diagram of the two-dimensional photonic crystal multiplexer/demultiplexer of the comparative example.
  • FIG. 8 is a graph showing the result of calculating the multiplex/demultiplex spectrums of the two-dimensional photonic crystal multiplexers/demultiplexers of the aforementioned embodiment and the comparative example, using the mode coupling theory.
  • FIG. 9 shows the result of calculating the multiplex/demultiplex spectrum of the two-dimensional photonic crystal multiplexer/demultiplexer, using the finite difference time domain (FDTD) method.
  • FDTD finite difference time domain
  • FIG. 10 is a plan view of a two-dimensional photonic crystal multiplexer/demultiplexer as another embodiment.
  • FIG. 11 is a schematic diagram showing another embodiment of the two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention.
  • FIG. 12 is a plan view of an embodiment of the two-dimensional photonic crystal multiplexer/demultiplexer having a heterostructure.
  • FIG. 13 is a chart showing the transmission wavelength band of the waveguide of the two-dimensional photonic crystal multiplexer/demultiplexer having a heterostructure.
  • FIG. 5A is a perspective view and FIG. 5B is a plan view of an embodiment of the two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention.
  • the body 21 which is slab shaped, is provided with modified refractive index areas created by boring holes 22 in a triangular lattice pattern with cycle a.
  • This body has an input waveguide 23 and an output waveguide 24 , each of which is formed by linearly eliminating the holes 22 , or omitting the formation of the holes 22 , along a single line.
  • the distances between the input waveguide 23 and the point-like defect 25 and between the point-like defect 26 and the output waveguide 24 each correspond to five lines of the holes 22 : (5/2) ⁇ 3 0.5 a.
  • the distance between the two point-like defects 25 and 26 is 4 ⁇ 3 0.5 a .
  • the following calculation assumes that a is 420 nm and the diameter of the hole 22 is 240 nm.
  • the two point-like defects and the two waveguides are symmetrically arranged with respect to a point.
  • the point-like defects 25 and 26 are each formed by omitting three holes 22 lying on a straight line. Being entirely constituted by the same material as that of the body 21 , these point-like defects can easily confine light because there is a difference in refractive index between the body 21 and the surrounding air. Therefore, these point-like defects prevent light from leaking from the surface of the body 21 to the outside, thus yielding a high level of Q-value.
  • two holes 221 and 222 closest to the point-like defects are each shifted to a position 0 . 15 a farther from the point-like defect than the position shown in FIG. 6A where each hole is located at a triangular lattice point.
  • the parameters relating to the two-dimensional photonic crystal multiplexer/demultiplexer of the present embodiment can be calculated using the finite difference time domain method (FDTD method) as follows: Q in , the Q-value between the input waveguide 23 and the point-like defect 25 as well as between the point-like defect 26 and the output waveguide 24 , is Q in ⁇ 3590; and ⁇ , the mutual coupling coefficient between the point-like defects 25 and 26 , is ⁇ ⁇ 1.42 ⁇ 10 ⁇ 4 ⁇ 0 . From these values, the coupling ratio is derived as 0.90, which falls within the aforementioned preferable range: 0.2 to 10. Also, the resonance wavelength ⁇ 0 of the point-like defects 25 and 26 is 1581.6 nm.
  • FDTD method finite difference time domain method
  • Comparative Example 1 ( FIG. 7A ): a two-dimensional photonic crystal multiplexer/demultiplexer having only one point-like defect 31 , which construction corresponds to the present embodiment with one of the point-like defects eliminated; and Comparative Example 2 ( FIG. 7B ): a two-dimensional photonic crystal multiplexer/demultiplexer having only one point-like defect 32 equally spaced from both the input waveguide 23 and the output waveguide 24 by a distance of (5/2) ⁇ 3 0.5 a .
  • the results of the calculations are shown in FIG. 8 .
  • the ordinate indicates the multiplex/demultiplex spectrum I( ⁇ ) in decibels:
  • I dB 10 ⁇ log[I( ⁇ )/I( ⁇ 0 )].
  • the multiplex/demultiplex spectrum 40 of the present embodiment has the following features:
  • the multiplex/demultiplex spectrum of the present embodiment takes larger values than the comparative examples, showing a flattop shape.
  • the wavelength range where I dB is equal to or larger than ⁇ 1 dB i.e. I( ⁇ ) ⁇ 0.79I( ⁇ 0 )
  • I( ⁇ ) ⁇ 0.79I( ⁇ 0 ) is 0.25 nm for the multiplex/demultiplex spectrum 41 of Comparative Example 1, 0.45 nm for the multiplex/demultiplex spectrum 42 of Comparative Example 2, and 0.43 nm for the present embodiment, which is larger than the value of Comparative Example 1. Therefore, even if the resonance wavelength ⁇ 0 is displaced from the original value due to an error of a light generator or some other factor, the loss is smaller in the present embodiment than in Comparative Example 1.
  • the multiplex/demultiplex spectrum takes a smaller value in the present embodiment than in any other comparative examples, showing a shorter tail.
  • the wavelength range where I dB equals to ⁇ 20 dB i.e. I( ⁇ ) ⁇ 0.01I( ⁇ 0 )) is 2.01 nm wide in the present embodiment; this width is smaller than 4.8 nm of Comparative Example 1 or 9.2 nm of Comparative Example 2.
  • the construction of the present embodiment can reduce the noise caused by signals within the wavelength range far from the resonance wavelength ⁇ 0 and suppress the crosstalk with signals from other channels.
  • the above-described calculation method using the mode coupling theory is advantageous in that the multiplex/demultiplex spectrum can be derived using function formulae.
  • the method is easily affected by an error in Q-value or mutual coupling coefficient ⁇ . Therefore, additional calculations have been conducted using the FDTD method, which numerically determines the multiplex/demultiplex spectrum without computing the Q-value or ⁇ .
  • the result is as shown in FIG. 9 by filled circles.
  • the multiplex/demultiplex spectrum obtained is narrower than that calculated using the mode coupling theory, it also shows a flattop shape at around the resonance wavelength ⁇ 0 and a short tail stretched over the wavelength range far from the resonance wavelength ⁇ 0 , as in the result of the calculation using the mode coupling theory.
  • the multiplex/demultiplex spectrum has been calculated using the FDTD method for the case where the point-like defect 26 is shifted in the direction perpendicular to the waveguide by (7/2) ⁇ 3 0.5 a and in the longitudinal direction of the waveguide by 1.5 a with respect to the point-like defect 25 .
  • the result is as shown in FIG. 9 by triangles.
  • the two sets of data shown in FIG. 9 suggests that the construction of FIG. 10 having larger values at around the resonance wavelength is preferable if the discrepancy of the resonance wavelength ⁇ 0 is regarded as more important, whereas the construction of FIG. 5 is recommendable if the suppression of the noise or crosstalk is more important.
  • the optical output section of the demultiplexer is constructed as the output waveguide 24 . It is also possible to construct it as a point-like defect. This point-like defect also functions as the input section of a multiplexer.
  • the output section of the demultiplexer (or the input section of the multiplexer) consists of a point-like defect 51 formed by omitting three holes 22 lying on a line, similar to the point-like defects 25 and 26 .
  • the holes closest to the point-like defect 51 are arranged at positions closer to the corresponding triangular lattice points than in the case of the point-like defects 25 and 26 .
  • This arrangement makes the Q-value of the point-like defect 51 smaller than that of the point-like defect 25 or 26 .
  • the light extracted from the input waveguide 23 is transmitted through the point-like defects 25 and 26 and emitted from the body surface of the point-like defect 51 having the reduced Q-value to the outside of the crystal.
  • the two-dimensional photonic crystal multiplexer/demultiplexer according to the present invention can take various forms: the point-like defect may be differently shaped, such as a hole having a different diameter; and the holes may be arranged in a different cyclic pattern, such as a square lattice pattern.
  • FIG. 12 shows an embodiment of the two-dimensional photonic crystal multiplexer/demultiplexer provided with reflecting sections at the first and second optical input/output sections, respectively, and having a heterostructure.
  • the body 61 consists of two forbidden band zones 63 and 64 .
  • the input waveguide 65 and the output waveguide 66 which are identically shaped, pass through the two forbidden band zones 63 and 64 .
  • the cycle of the holes 62 is a 1 for the forbidden band zone 63 and a 2 for the forbidden band zone 64 , where a 1 >a 2 .
  • Two point-like defects 67 and 68 having the same shape are located between the input waveguide 65 and the output waveguide 66 .
  • the transmission wavelength band of the waveguide in the two forbidden band zones is as shown in FIG. 13 .

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Nanotechnology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Integrated Circuits (AREA)
US10/566,843 2003-08-29 2004-08-24 Two-dimensional photonic crystal multiplexer/demultiplexer Expired - Fee Related US7406221B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2003307654A JP3763826B2 (ja) 2003-08-29 2003-08-29 ２次元フォトニック結晶分合波器
JP2003307654 2003-08-29
PCT/JP2004/012114 WO2005022219A1 (fr) 2003-08-29 2004-08-24 Multiplexeur/demultiplexeur bidimensionnel

Publications (2)

Publication Number Publication Date
US20060204161A1 US20060204161A1 (en) 2006-09-14
US7406221B2 true US7406221B2 (en) 2008-07-29

Family

ID=34269454

Family Applications (1)

Application Number Title Priority Date Filing Date
US10/566,843 Expired - Fee Related US7406221B2 (en) 2003-08-29 2004-08-24 Two-dimensional photonic crystal multiplexer/demultiplexer

Country Status (8)

Country Link
US (1) US7406221B2 (fr)
EP (1) EP1659431B1 (fr)
JP (1) JP3763826B2 (fr)
KR (1) KR101116736B1 (fr)
CN (1) CN100394228C (fr)
CA (1) CA2537206C (fr)
TW (1) TW200513696A (fr)
WO (1) WO2005022219A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080101800A1 (en) * 2006-10-26 2008-05-01 Edo Waks Dipole induced transparency drop-filter cavity-waveguide system
US20100104250A1 (en) * 2007-03-26 2010-04-29 Kyoto University Two-dimensional photonic crystal
US20130105927A1 (en) * 2010-01-07 2013-05-02 Kyoto University Photoelectric conversion element
US9324891B2 (en) 2010-01-07 2016-04-26 Sharp Kabushiki Kaisha Solar cell, solar cell panel, and device comprising solar cell
US20220350220A1 (en) * 2019-09-20 2022-11-03 Humboldt-Universitaet Zu Berlin Device for generating individual photons

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006267474A (ja) * 2005-03-23 2006-10-05 Kyoto Univ フォトニック結晶
CN101430277B (zh) * 2007-11-07 2010-09-29 清华大学 气体折射率传感器
CN100510813C (zh) * 2007-12-03 2009-07-08 中国科学院光电技术研究所 一种高耦合效率的复合型二维光子晶体的设计方法
CN101458210B (zh) * 2007-12-12 2012-09-19 清华大学 折射率传感器
EP2506046A1 (fr) * 2011-03-31 2012-10-03 Alcatel Lucent Multiplexeur optique
JP6106107B2 (ja) * 2014-02-12 2017-03-29 日本電信電話株式会社 光共振器
CN111856656B (zh) * 2020-07-24 2022-12-23 上海大学 一种光子晶体结构的四信道下路滤波器
CN112747820B (zh) * 2020-12-23 2022-03-25 南京大学 一种集成硅光子晶体波导的太赫兹探测器

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62100706A (ja) 1985-10-28 1987-05-11 Nippon Telegr & Teleph Corp <Ntt> 光リングフイルタ
WO1998057207A1 (fr) 1997-06-09 1998-12-17 Massachusetts Institute Of Technology Filtre de transfert de canaux a haute efficacite a commutation et modulation commandees par l'absorption
WO2001020379A1 (fr) 1999-09-15 2001-03-22 Ho Seng Tiong Transistors a photons
JP2001228347A (ja) 2000-02-16 2001-08-24 Japan Science & Technology Corp 光導波路型波長フィルタ
JP2001272555A (ja) 2000-03-24 2001-10-05 Kansai Tlo Kk ２次元フォトニック結晶導波路、および波長分波器
US20020191905A1 (en) 2001-06-11 2002-12-19 Prather Dennis W. Multi-channel wavelength division multiplexing using photonic crystals
US20030011775A1 (en) 2001-05-15 2003-01-16 Marin Soljacic Mach-Zehnder interferometer using photonic band gap crystals
FR2841658A1 (fr) 2002-06-26 2004-01-02 Centre Nat Rech Scient Dispositif de couplage optique directionnel et selectif en longueur d'onde
WO2004068205A1 (fr) 2002-12-26 2004-08-12 Japan Science And Technology Agency Filtre de frequences electromagnetiques

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1156063C (zh) * 2000-06-06 2004-06-30 中国科学院物理研究所 一种光子晶体微腔结构
US6832033B2 (en) * 2001-06-11 2004-12-14 The University Of Delaware Hetero-structure photonic bandgap materials

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62100706A (ja) 1985-10-28 1987-05-11 Nippon Telegr & Teleph Corp <Ntt> 光リングフイルタ
WO1998057207A1 (fr) 1997-06-09 1998-12-17 Massachusetts Institute Of Technology Filtre de transfert de canaux a haute efficacite a commutation et modulation commandees par l'absorption
WO2001020379A1 (fr) 1999-09-15 2001-03-22 Ho Seng Tiong Transistors a photons
JP2001228347A (ja) 2000-02-16 2001-08-24 Japan Science & Technology Corp 光導波路型波長フィルタ
JP2001272555A (ja) 2000-03-24 2001-10-05 Kansai Tlo Kk ２次元フォトニック結晶導波路、および波長分波器
US20030011775A1 (en) 2001-05-15 2003-01-16 Marin Soljacic Mach-Zehnder interferometer using photonic band gap crystals
US20020191905A1 (en) 2001-06-11 2002-12-19 Prather Dennis W. Multi-channel wavelength division multiplexing using photonic crystals
FR2841658A1 (fr) 2002-06-26 2004-01-02 Centre Nat Rech Scient Dispositif de couplage optique directionnel et selectif en longueur d'onde
US20050152649A1 (en) 2002-06-26 2005-07-14 Centre National De La Recherche Scientifique And Ecole Polytechnique Device for directional and wavelength-selective optical coupling
WO2004068205A1 (fr) 2002-12-26 2004-08-12 Japan Science And Technology Agency Filtre de frequences electromagnetiques

Non-Patent Citations (12)

* Cited by examiner, † Cited by third party
Title
Akahane et al; 1p-ZM-3; "Optical Add/Drop Devices Using 2D Photonic Crystal-Design of device structures to achieve flat-top transfer function in filtering responses"; 2003; p. 944.
Akahane et al; 29a-YN-9; "Drastic Increase of Quality Factor of Defect-Cavities in 2D Photonic Crystal Slabs by Modifying Defect Structure"; Mar. 2003; p. 1138.
B.E. Little et al; "Microring Resonator Channel Dropping Filters"; Journal of Lightwave Technology; vol. 15, No. 6, Jun. 1997; pp. 998-1005.
B.S. Song et al; 29a-YN-4; "Improvement of Optical Add/Drop Filtering efficiency by using an In-Plane Hetero structure Interface"; Mar. 2003; p. 1137.
Bong-Shik Song et al; "Photonic Devices Based on In-Plane Hetero Photonic Crystals"; Science; vol. 300; Jun. 6, 2003; p. 1537, right column, lines 1-9, Fig. 1D.
Jin, Chongjun et al; "Reflectionless Multichannel Wavelength Demultiplexer in a Transmission Resonator Configuration", IEEE Journal of Quantum Electronics, vol. 39, No. 1, Jan. 2003, pp. 160-161.
M.J. Khan et al; "Mode-Coupling Analysis of Multipole Symmetric Resonant Add/Drop Filters"; IEEE Journal of Quantum Electronics; Oct. 1999; vol. 35; No. 10; pp. 1451-1460.
S. Fan et al; "Channel Drop Tunneling through Localized States"; Physical Review Letters; The American Physical Society; Feb. 2, 1998; vol. 80, No. 5; pp. 960-963.
Y. Akahane et al; "High-Q photonic nanocavity in a two-dimensional photonic crystal"; Nature Publishing Group; Oct. 30, 2003; vol. 425; pp. 944-947.
Y. Sugimoto et al; "Design, fabrication, and characterization of coupling-strength-controlled directional coupler based on two-Dimensional photonic-crystal slab waveguides"; Applied Physics Letters; Oct. 20, 2003; vol. 83, No. 16; pp. 3236-3238.
Yoshihiro Akahane et al; "Design of a channel drop filter by using a donor-type cavity with high-quality factor in a two-dimensional photonic crystal slab"; Applied Physics Letters; vol. 82, No. 9; Mar. 3, 2003; pp. 1341-1343.
Yoshimasu Sugimoto et al; 29a-YN-5; "Design and characteriziation of coupling-controlled directional coupler (CC-DC) Based on photonic-crystal FESTA"; Mar. 2003; p. 1137.

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080101800A1 (en) * 2006-10-26 2008-05-01 Edo Waks Dipole induced transparency drop-filter cavity-waveguide system
US7630604B2 (en) * 2006-10-26 2009-12-08 The Board Of Trustees Of The Leland Stanford Junior University Dipole induced transparency drop-filter cavity-waveguide system
US20100135612A1 (en) * 2006-10-26 2010-06-03 Edo Waks Optical switching based on dipole induced transparency
US7848603B2 (en) * 2006-10-26 2010-12-07 The Board Trustees Of The Leland Stanford Junior University Optical switching based on dipole induced transparency
US20100104250A1 (en) * 2007-03-26 2010-04-29 Kyoto University Two-dimensional photonic crystal
US8126306B2 (en) * 2007-03-26 2012-02-28 Kyoto University Two-dimensional photonic crystal
US20130105927A1 (en) * 2010-01-07 2013-05-02 Kyoto University Photoelectric conversion element
US9324891B2 (en) 2010-01-07 2016-04-26 Sharp Kabushiki Kaisha Solar cell, solar cell panel, and device comprising solar cell
US20220350220A1 (en) * 2019-09-20 2022-11-03 Humboldt-Universitaet Zu Berlin Device for generating individual photons
US11556045B2 (en) * 2019-09-20 2023-01-17 Humboldt-Universitaet Zu Berlin Device for generating individual photons

Also Published As

Publication number Publication date
CA2537206A1 (fr) 2005-03-10
US20060204161A1 (en) 2006-09-14
CN100394228C (zh) 2008-06-11
WO2005022219A1 (fr) 2005-03-10
JP3763826B2 (ja) 2006-04-05
TW200513696A (en) 2005-04-16
EP1659431B1 (fr) 2012-05-09
CN1846156A (zh) 2006-10-11
KR101116736B1 (ko) 2012-02-22
EP1659431A1 (fr) 2006-05-24
KR20060033800A (ko) 2006-04-19
JP2005077709A (ja) 2005-03-24
EP1659431A4 (fr) 2007-06-27
TWI359290B (fr) 2012-03-01
CA2537206C (fr) 2012-05-15

Similar Documents

Publication Publication Date Title
US7406221B2 (en) Two-dimensional photonic crystal multiplexer/demultiplexer
US7590325B2 (en) Two-dimensional photonic crystal optical multiplexer/demultiplexer
KR100739522B1 (ko) 전자기파 주파수 필터
US7738749B2 (en) Photonic crystal having heterostructure and optical device using the photonic crystal
EP1577686B1 (fr) Filtre de frequences electromagnetiques
EP1666939B1 (fr) Resonateur cristal photonique bidimensionnel
US7116878B2 (en) Optical waveguide structure
JPH11271541A (ja) 波長分波回路
US6539150B2 (en) Segmented waveguide flattening the passband of a phasar
JP4171326B2 (ja) ２次元フォトニック結晶中の共振器と波長分合波器
US7796849B2 (en) Spatial separation of optical frequency components using photonic crystals
JPS61284707A (ja) 光合分波器
KR20160115573A (ko) 배열 도파로 격자 소자 및 그 제조 방법
JP2006267474A (ja) フォトニック結晶
JPS61284705A (ja) 光合分波装置
KR20170013802A (ko) 플라즈모닉 소자
GB2393264A (en) Optical photonic crystal waveguide filter

Legal Events

Date Code Title Description
AS Assignment

Owner name: SUMITOMO ELECTRIC INDUSTRIES, LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:NODA, SUSUMU;ASANO, TAKASHI;AKAHANE, YOSHIHIRO;REEL/FRAME:017547/0264;SIGNING DATES FROM 20051219 TO 20051222

Owner name: JAPAN SCIENCE AND TECHNOLOGY AGENCY, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:NODA, SUSUMU;ASANO, TAKASHI;AKAHANE, YOSHIHIRO;REEL/FRAME:017547/0264;SIGNING DATES FROM 20051219 TO 20051222

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FEPP Fee payment procedure

Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

LAPS Lapse for failure to pay maintenance fees

Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20200729